Recently, the demand for portable electronic products such as notebook computers, video cameras and portable telephones has increased sharply, and electric vehicles, energy storage batteries, robots, satellites and the like have been developed in earnest. Accordingly, high-performance secondary batteries allowing repeated charging and discharging are being actively studied.
Secondary batteries commercially available at the present include nickel-cadmium batteries, nickel hydrogen batteries, nickel-zinc batteries, lithium secondary batteries and the like. Among them, the lithium secondary batteries are in the limelight since they have almost no memory effect compared to nickel-based secondary batteries and also have very low self-discharging rate and high energy density.
In recent years, secondary batteries have been widely used not only in small-sized devices such as portable electronic devices but also in medium-sized and large-sized devices such as vehicles and power storage devices. In particular, as carbon energy is getting depleted and the interest in the environment is increasing, the attention is focused on hybrid electric vehicles and electric vehicles around the world including the US, Europe, Japan and Korea. The most important component of the hybrid electric vehicles and electric vehicles is a battery pack that gives a drive power to a vehicle motor. Since the hybrid electric vehicle or electric vehicle is able to obtain a driving force of the vehicle through charging and discharging of the battery pack, the fuel efficiency is higher than that of a vehicle using only an engine, and pollutants may be reduced or substantially eliminated. For these reasons, the hybrid electric vehicles and electric vehicles are used more and more. In addition, the battery pack of the hybrid electric vehicle or electric vehicle includes a plurality of secondary batteries, and the plurality of secondary batteries are connected in series and in parallel to improve capacity and power.
Meanwhile, in addition to the secondary battery, the battery pack includes various components such as a battery management system (BMS), a sensing component for measuring an electrical signal of the secondary battery, an elastic component for controlling the swelling of the secondary battery, and a coupling member for coupling plates surrounding the battery pack.
In a conventional battery pack, a plurality of battery cell groups, in each of which a plurality of secondary batteries are stacked, are arranged to configure a cell assembly, and spaces accommodating the BMS, the sensing component, the elastic component and the coupling component as described above are separately partitioned around the cell assembly.
When the conventional battery pack requires a specification for ensuring a maximum energy capacity in a narrow space, since the space is partitioned to accommodate various components around the cell assembly as described above, the energy density may be lowered.